Genetics in Orthodontics

Good morning
Gregor Johann Mendel
www.indiandentalacademy.com

Genetics in
orthodontics www.indiandentalacademy.com

Conten
t
2.Principle of genetic transmission
3. Aetiological heterogenecity
4 .population genetics
5.Hereditory in craniofacial complex .
a) general principle.
b) dentition
c) skeleton
6. Syndrome
7. Twins study
1. Terminology

Terminology
GENE : The term gene was introduced by Johannsen in 1909
Gen = Being born, producing, coming to be.
Gene is the structural and functional unit of hereditary which occupies a specific place (locus)
on a chromosome). It is capable of reproducing itself exactly at each cell division and ducts
formation of enzyme or protein.
Homozygote : If alleles are like, and is homozygous for that gene concern.
Heterozygote : If alleles are dissimilar.
Genotype : the genetic make up of an individual.
Phenotype : External manifestation which genes produce. observable properties, measurable feature
Congenital : Present at time of birth.
MUTATION : Mutation is defined as a change in genetic construction from one stable form to
another stable form. The first mutation was recognized by T.H. Morgan in
Drosophila Melanogaster or fruit fly in1910.
Genome : the genome contain entire genetic content of a set of choromosome present with in a cell
or in organism.

You may have had a very illustrious great great grand
Father ; but by the law of chance you have received
Only about 1/16 of your gene from him. You received
as just as many gene from the horse thieves , gamblers
And other undesirable who may have been in that
Generation of your family tree.
A.M.WINCHESTER

GENE (DNA)
RNA FORMATION
PROTEIN FORMATION
CELL STRUCTURE
CELL ENZYME
CELL FUNCTION

Dominant inheritance
A dominant can be recognized from the following characteristics:
1) Every diseased person has a parent who manifests the disease
2) The disease appears in every generation.
3) Unaffected persons cannot transmit the disease.
4) When a diseased person marries a normal individual the chance
of the children being normal or diseased are equal.
In higher form of life inheritance does not occur in such mathematical ratio as Mendel found in peas
by T.H. MORGAN.www.indiandentalacademy.com

Recessive inheritance
Recessive can be recognized from the following characteristics
More than one brother and sister may be affected .
The abnormality is more commonly seen in children resulting
Diseased individuals generally have parents who are normal
from marriage between close relatives.
Diseased person who marry normal individuals usually have
normal children
If two diseased person marry ,all their children affected

Aetiological heterogeneity
Etiology may have a variation .it may have a multifactorial basis so
that different patient are not necessarily affected for the same reason.
eg: no single cause can be identified in cleft lip pt or vander woude
syndrome.
It may be associated with environment teratogen such as alcohol ,
cigarette smoke and anticonvulsant drugs .

Population genetics
h chromosome carries hundred or thousand of genetics in a lin
and there is intra species specificity in the gene order. The s
osome contain same gene , chromosome map can be constructe
nable studies of genetic linkage and association .
rm mostly used in population genetics.
trance
essivity

Twins study
a) Dizygotic twins b) monozygotic
twins

Facial development in the embryo is demarcated by the appearance of
plate (the cranial end of the embryo) on the fourteenth day of develop
One of the most unusual features of vertebrate facial development is
of the facial mesenchyme which arises from nural crest cells. Migratio
Of neural crest cells are extremely important in facial develop-ment .
the derivatives of cephalic neural crest cells are the maxilla, mandib
nasal bones, and bones of the cranial vault .Although the cessation o
cell migration and the factors that cause neural crest cells to localize
regions are notyet completely understood, their migration into the bra
occurs in a highly regulated manner. This process is presumed to be u
control of genes known as homeobox genes, which endowneural crest
with a positional identity, which mediates aspects of craniofacial mo
and patterning.
Craniofacial development in embryo

specific homeobox genesMsx-1 and Msx-2 appear to be involved in
ial- mesenchymal interactions, and are implicated in cranio -facial
pment, and in particular in the initiation, developmental position (Msx
ther development(Msx-2) of the tooth buds
Control of tooth development
enesis imperfecta (AI): this is a group of genetically heterogeneous dis
ng enamel formation .It is clinically heterogeneous in that hypoplastic,
d And hypomaturation ; and genetically heterogeneous with familie se
ng autosomal dominant,autosomal recessiveand X-linked inheritance .
he prevalenceappears to vary quite significantly between 1:14,000 and
an and Holm,1986). In humans, two amelogenes, AMGX and AMGY,h
oned and mapped to the X and Y chromosomes,respectively (Lau et al.,
1997MacDougall et al. mapped the ameloblastin gene within thecritica
or autosomal dominant AI at chromosome4q21. It is likely, however,
tations in several genes may be involved in the aetiology of different
mally inherited AI.

Dentinogenesis imperfecta (DI): this is autosomaldominant and occu
approximately 1:8000 live births. Itpresents with brownish discolour
teeth, crownssusceptible to rapid attrition, fragile roots and pulp cha
obliteration due to abnormal continuous productionof dentine matrix
Presents a number of sub-types, one of which is coupled withosteogen
in which there is an alteration intype 1 collagen genes. Most patients
Of dentinogenesis imperfecta have mutations and deletions for amino
substitutions in genes with encode forsub-units of type 1 collage. The
defects in the collagen type 1 molecules affects the extra cellular mat

malocclusion
dy of craniofacial relationship in twin’s has provided much use full
rmation consering the role of hereditory in maloclusion
11 division 1: extensive cephalometric studies have been carried out to
mine the heritability of this trait.
w that in the class 11 div 1 pt. the mandible is significantlymore retru
n class 1 pt., with the body of the mandible smaller and over all mand
h reduced.
onmental factor can also contribute to the etiology of class 11 div 1
clution.

Angle’s class II division 2
Angel’s class 11 division 2 malocclusion , recognizes a unique
combination of
overbite, incisor Retroclination and sagittal discrepancy. A very
severe 11/2
phenotype characterized by concealment of the mandibular incisor’s
in
malocclusion , has been called deskbiss in German or cover bite.
x ray cephalometric and odontometric measurement were recorded for
subject and
data were compared from the control sample .which indicate the
presence of strong
genetic influence in the formation of angle’s class 11 division 2 deep
bite discrepancy.
ss or coverbite : At least one maxillary central incisor had to exhibit complete vertic
e to the corresponding mandibular incisor’s clinical crown in centric occlusion .

Class III.malocclusion.
Relative contribution of genetic and environmenal factor to class111 has been the
ubject of the Number of previous studies. A class 111 malocclusion resulting from
a skeletal imbalance betweenthe maxilary and mandibular bases may result from
deficiency in maxillary growth ,excessive Mandibular growth or a combination
f both. A wide range of environmental factor have also been suggested as
ontributory to the development of mandibular prognathism
1. Enlarge tonsil
2. Nasal blockage
3. Congenital anatomical defects .
4. Hormonal disturbance.
5. Endocrinal imbalance.
6. Posture
7. trauma

Hapsburg jaw
(mandibular prognathism)
(contemporary treatment of dentofacial deformity by proffit white and
sarver,

BUTLER’S FIELD THEORY
malian dentition can be divided into several developmental fields .
evelopment fields include the molar / premolar field the canine $ the i
.
al variability manifest itself strongly itself in distal region than in th
l direction .
lateral incisor is more prone to variation than the central incisor.

and Non Genetic Diseases which are Potentially be treated by gene th
ne deficiency
cholestrolamia
philia
r's disease
olysaccharidosis
ema
brosis
mtoid arthritis and many other

Methods of Gene Therapy :
1.Viral Agents – A number of different virus can be used to transport
foreign genetic material.
a) Retroviruses
b) Herpes viruses
Physical Agents
a) Liposome mediated DNA transfer
b) Receptor mediated endocytosis
c) Oligonucleotides

Syndrome
me of dentofacial disturbance of genetic origin can briefly
e listed .
gnathia
ognathia
palate and cleft lip
n’s syndrome ( 21 Trisomy)
ner’s syndrome
an’s syndrome
bism
o cranial dysplasia
ibulo facial dyostosis
ogenesis imperfecta
axillary protrusion. www.indiandentalacademy.com

Bimaxillary atresia
Retarded eruption of teeth
Hypodontia ,anodontia ,and oligodontia.
Abnormal over jet and overbite.
Open bite
High arched palate
Abnormal occlusion and arrangement of teeth

Syndrome on the basis of inheritance
Dominant
1. vander woude syndrome
2. treacher collin syndrome
3. clido cranial dysplasia
4. ecto dermal dysplasia
5. sticklens syndrome
Recessive
1. robert syndrome
2. appelt’s syndrome
3. christian syndrome
4. meckel syndrome

The changing concept : the genetic concept.
The assumption was made that the cartilages and facial suture
Were under genetic control. and that the brain determine the vault
Dimension.in1960 moss formulated functional matrix hypothesis.
Which provide logical frame work for an emerging concept.

CONCLUSION :
Genetics, always fascinated mankind. The first thinking ancestors of humans
were curious about the matters of inheritance. Early attempts to unravel the
mystery of genetics were simply hamper by lack of knowledge and understand of
basic processes.
Today, it is a known fact that every process of growth from multiplication to cell
death is ultimately controlled by genes .The quest for understanding of how genetic
factor contribute to disease, is gathering speed unraveling this network of events
will undoubtfully be challenge for sometime.
A large number of genetic disorders have oral manifestation and we as dental
practitioner should be able to recognize them.

references
1.(contemporary treatment of dentofacial deformity by proffit white and sarver, 2) The
development of dentofacial deformity ; influence and etiologic factor, page 55.)
DO Volume 1957 Dec (891 - 918):
A critical analysis of orthodontic concept and objectives - Wilson
complex genetics of cleft lip and palate (Martyn T. Cobourne)
Division of Orthodontics and Craniofacial Development, GKT Dental Institute, London,UK
eritability of Malocclusion: Part 2. The Influence of Genetics in Malocclusion
P. A. Mossey, B.D.S., Ph.D., D.Orth. (R.C.S. Ed.), M. Orth. (R.C.S.
Eng.), F.F.D. (R.C.S.I.)
nd book of orthodontics by robert e moyers, dds, phd
e angle’s orthodontics vol 68 no1 1998 , page 9.
Thank you
7. Bjo march 1999 vol 26 no1 , 21
-28
8. Bjo /vol26/ 1999/195-203
9.Bjo /vol26/1999/103-113

Bjo march 1999 vol 26 no1 ,

Genetics in Orthodontics

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